We have studied the unbound levels of ${}_{}{}^{137}{}_{}{}^{}\mathrm{Xe}$ via neutron resonance reactions and β decay of ${}_{}{}^{137}{}_{}{}^{}\mathrm{I}$. High-resolution neutron transmission data revealed a total of 35 resonances below a neutron energy of 500 keV. At least 27 of the resonances are p-wave resonances. The near absence of s-wave resonances in this energy region resulted in an extremely low value for the s-wave neutron strength function. The current γ-ray data complement earlier studies of γ rays and delayed neutrons following the β decay of ${}_{}{}^{137}{}_{}{}^{}\mathrm{I}$. By combining all data, we have obtained a detailed picture of the level density in ${}_{}{}^{137}{}_{}{}^{}\mathrm{Xe}$ for a wide range of angular momenta. With the exception of ${\mathrm{}(1/2)\mathrm{}}^{+}$ and ${\mathrm{}(1/2)\mathrm{}}^{\mathrm{-}}$ levels, the overall agreement is good between the current data and predictions of the Fermi gas model.

The inelastic cross sections and analyzing powers for spin excitations in ${}_{}{}^{40}{}_{}{}^{}$,48Ca have been measured at $E_{\mathrm{p}}$=334 MeV. The data for excited states in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at 8.424 MeV ($2^{\mathrm{-}}$) and 10.31 MeV ($1^{+}$) and the 10.22-MeV ($1^{+}$) state in ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$ are fairly well described by microscopic distorted-wave impulse approximation calculations. Normalizations of the calculated cross sections to the experimental data show that these spin excitations are quenched. We deduce B(M2)↑=281 ${\mu }_{\mathrm{N}}^2$${\mathrm{fm}}^2$ for the 8.42-MeV $2^{\mathrm{-}}$ state in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$.

Results of a search for M1 strength in the N=28 isotones ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$, and ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$ by means of high-resolution electron scattering are presented. The M1 strength investigated in the energy region $E_x$≃7–12 MeV is found to be strongly fragmented and considerably suppressed with respect to results from shell-model calculations which include up to 2p-2h excitations. The theoretical model is also compared with recent results using other experimental probes.

It was suggested recently that the level schemes of the odd Hg isotopes with 193≤A≤199 could be described in the framework of the U(5) limit of the U(6/12) supersymmetry scheme. This suggestion has been further tested using the reactions ${}_{}{}^{200}{}_{}{}^{}$,198,196Hg(p,d${)}^{199}$,197,195Hg. The comparison of the experimental spectroscopic factors with the ones computed using the U(6/12) model shows that among the three nuclei studied, ${}_{}{}^{195}{}_{}{}^{}\mathrm{Hg}$ and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Hg}$ can be considered as reasonably described. The agreement in this case with U(6/12) is better in the U(5) limit than in the O(6) limit.

Angular distributions and angle-integrated (θ=0°–90°) cross sections are presented for 48 levels (or groups of levels) in the excitation-energy range 4.5–8.5 MeV in the reaction ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$${(}^7$Li,p${)}^{20}$F, at a bombarding energy of E${(\mathrm{}}^7$Li) = 16.0 MeV. Many levels are candidates for having high J. Measured cross sections, together with previous information, enable unique $J^{\pi }$ assignments in a few cases for low-J states.

Elastic and inelastic scattering of ${}_{}{}^{12}{}_{}{}^{}$C${+\mathrm{}}^{12}$C, especially excitations of the ground-rotational-band members in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, have been studied at 139.5 and 158.8 MeV. Although reasonable fits to the angular distributions for the band members were obtained with a shallow optical potential, rainbowlike gross bumps observed at large angles in the elastic scattering were not explained at all by coupled-channel calculations for the rotational band. The present results of ‖${\beta }_2$R‖ and ‖${\beta }_4$R‖ obtained by the coupled-channel calculations are in good agreement with previously reported results, except some from ${}_{}{}^{12}{}_{}{}^{}$C${+\mathrm{}}^{12}$C scattering. These analyses indicate a significant difference in the deformation lengths derived depending upon the signs of the deformations. The sign of the deformation parameters is also discussed.

The properties of high-spin states in ${}_{}{}^{199}{}_{}{}^{}$,201Bi have been studied with the ${}_{}{}^{194}{}_{}{}^{}$,196Pt${(}^{10}$B,5nγ )${}^{199}$,201Bi reactions at energies between 57 and 72 MeV. In-beam measurements of γ-ray excitations, γ-γ-t coincidences and correlations, γ-ray angular distributions, and pulsed-beam-γ timing were performed with Ge detectors to determine level energies, decay schemes, γ-ray multipolarities, $J^{\pi }$ assignments, and isomeric lifetimes. Levels along and near the yrast lines were established up to J≊(33/2), including a number of isomers. The systematic trends of three-quasiparticle level energies in odd-mass Bi isotopes have been extended and compared with calculations involving neutron-hole configurations of the Pb-core isotones. The transition strengths extracted for ${}_{}{}^{199}{}_{}{}^{}$,201Bi are compared to Pb-region values. In addition, an isomeric lifetime was measured in ${}_{}{}^{200}{}_{}{}^{}\mathrm{Bi}$.

It is shown that fission anisotropies from reactions with projectiles lighter than A=20 are well described by the standard theory, in which it is assumed that the distribution of K values (projection of total spin I onto the symmetry axis) is determined at the fission saddle point. Angular anisotropies of symmetric fragments from heavy ion reactions with projectiles heavier than A=24 are, however, substantially larger than expected on the basis of this theory, an observation which recently led to the suggestion that the K values adjust adiabatically during the descent from saddle to scission such that the observed final K distributions reflect a thermal equilibrium at the scission point. The predictions of such scission point models are compared with the available experimental data and it is shown that they fail to reproduce the observed trends as a function of bombarding energy for most systems. It is concluded that the observed deviation from the saddle point theory can be explained as a dynamical inhibition of complete fusion with heavy projectiles. An analysis is carried out in which the fraction of the symmetric fragment cross section originating from the fission decay of completely fused compound nuclei can be estimated. The systematics of the inhibition to complete heavy ion fusion is discussed in the framework of the extra push model.

The consequences of the formation of a quark-gluon plasma and its later hadronization are investigated. It is assumed that the plasma is formed beyond a specified energy density in the two reactions considered, the total annihilation of antinucleons on nucleons and the central collision of heavy ions. A coalescence model for the formation of quark clusters or hadrons is formulated. The multiplicity and momentum distribution of pions and kaons from nn¯ annihilation as also the ratio of the production of pions, kaons, and lambdas to protons are estimated for various collision energies of the heavy ions. The ${\mathrm{K}}^{+}$ spectra at three angles are computed and compared with available experimental data.

The effects of static and dynamic deformation on the heavy-ion elastic scattering quarter-point angle are discussed and analyzed in the sudden approximation. Simple expressions are derived within the Fresnel model and applications to several heavy-ion systems are presented.

In some heavy-ion reactions, such as ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$${(}^{16}$O${,}^{12}$C${)}^{28}$ Si oscillatory structure often appears in the whole angle region in the differential cross section. This anomalous phenomenon, unexpected from ordinary distorted-wave Born approximation theory, is explained by an alpha transfer process between two unidentical nuclear cores. Nuclear molecular-orbit theory has been formulated, and the coupled system of wave equations describing both the elastic scattering and transfer reaction channels are obtained. An independent α particle model is assumed in the evaluation of nuclear wave functions. The differential cross sections of both channels have been calculated simultaneously for two cases: ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$${(}^{16}$O${,}^{16}$O${)}^{24}$ Mg and ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$${(}^{16}$O${,}^{12}$C${)}^{28}$ Si as well as ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$${(}^{16}$O${,}^{16}$O${)}^{28}$ Si and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$${(}^{16}$O${,}^{12}$C${)}^{32}$ S. Agreement with the experimental data can be reached in the whole angle region for both of these cases.

A geometrical model is proposed for the distribution of matter in the ${}_{}{}^3{}_{}{}^{}\mathrm{-}_{}^3{}_{}{}^{}$He system, incorporating a short-range three-nucleon correlation. Charge symmetry violation is introduced through a distortion of this correlation in going from ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ to ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. The model is able to describe the charge-symmetry violating effects observed in ${\pi }^{\pm }$ scattering from these nuclei. When adjusted to fit the high $q^2$ behavior of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ charge form factor, the model yields a prediction for the corresponding structure in ${}_{}{}^3{}_{}{}^{}\mathrm{H}$.

We evaluate the angular distributions and the orientation asymmetry variable $A_S$(θ) in the description of pion scattering from oriented, deformed nuclei. The results show a strong, selective sensitivity of $A_S$(θ) to the neutron and proton deformation ${\beta }_2^N$ and ${\beta }_2^C$. We also evaluate the energy dependence of $A_S$(θ) and conclude that single charge exchange from ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$ at $T_{\pi }$=160 MeV would be an interesting case to study experimentally. Results of deformed Hartree-Fock calculations indicate $A_S$(θ)=6% for this nucleus.

The inclusive pion inelastic scattering and absorption for energies around the (3,3) resonance region are studied in a unified way using statistical transport models. A statistical expression is derived for the mean momentum of the protons in the (π,p) reaction, allowing comparison with recent rapidity measurements. Two one-dimensional models, one with π and one with π and Δ channels, are developed, which show the target mass and beam energy dependence of the inclusive cross sections with reasonable values for the input absorption parameters. The mean momentum calculated in the two models reproduces the (${\pi }^{+}$,p) rapidity data with a 2N absorption process, but not with larger clusters.

The ${\pi }^{\mathrm{-}}$ absorption by ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is investigated in a model study based on the nucleon pole mechanism πNN→NN→NN. We find that the amplitude of the three-body rescattering mechanism can have a strong interference effect with the amplitude of the direct two-body absorption process even in the region where the two-body process dominates. The main experimental signature of this important coherent effect is a sharp peak near the high energy end of the proton spectrum measured in a coincident experiment. Our results suggest that in order to extract the isospin dependence of pion absorption by a pair of nucleons from the recent ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(${\pi }^{\pm }$,NN) data, the three-nucleon rescattering amplitude must be calculated accurately and included coherently in the analysis.

The relative importance of various mechanisms which may play a role in the production of backward energetic protons has been studied in 800 MeV proton-nucleus collisions. Energetic protons (P≥350 MeV/c) at θ=118° were measured in coincidence with particles emitted in the angular range from 15° to 100°. Both in-plane (Δφ=180°) and out-of-plane (Δφ=90°) coincidences were measured. The data have been decomposed into several categories depending on the excitation energy of the residual nucleus. Momentum spectra, angular distributions, and target mass dependences of these categories have been studied. The scattering of the incident proton by a correlated nucleon cluster seems to play an important role. From the proton spectrum associated with the p-d quasi-elastic scatterings, the momentum spread of the pn system (‘‘d’’) inside the nucleus has been determined. The momentum spread of the ‘‘d’’ obtained by the p-d quasi-elastic scatterings is found to be smaller than the spread observed in heavy-ion projectile fragmentation into deuterons. From the mass dependence of the ratio of the p-d to p-p quasi-elastic scattering cross sections, the mean free path of deuterons inside the nucleus has been determined.

It is shown that conclusions can be drawn in regard to fundamental structure of nuclear material from the scattering of ${\mathrm{K}}^{+}$ mesons from nuclei. A calculation of the ratio ${\mathrm{K}}^{+}$-carbon to ${\mathrm{K}}^{+}$-deuteron total cross sections is presented which includes traditional medium corrections and their uncertainties. That this calculation falls well below the available data suggests more exotic mechanisms. In particular, models for the distribution of quarks involving an increased confinement range can be tested. Treatment of the ${\mathrm{K}}^{+}$ either via an optical model or in a multiple scattering expansion approach yields equivalent results.

The ${}_{}{}^{16}{}_{}{}^{}\mathrm{N}$($2^{\mathrm{-}}$,g.s.)→${}^{16}$O(0 ${}_{}{}^{+}{}_{}{}^{}$,g.s.)${+\mathrm{e}}^{\mathrm{-}}$+ν${¯}_{\mathrm{e}}$ branching ratio is remeasured. A flatfield magnetic spectrometer, instrumented with a multiwire position-sensitive proportional detector, is used. A value for the branching ratio ${\Gamma }_{\beta }$${(2\mathrm{}}^{\mathrm{-}}$→$0^{+}$)/${\Gamma }_{\beta }$${(2\mathrm{}}^{\mathrm{-}}$ )=0.2811±0.0064 is determined. Combining this result with another recent determination produces a best value for this branching ratio. This in turn allows a more precise determination of the beta-decay rate (${\Lambda }_{\beta }$) for the process ${}_{}{}^{16}{}_{}{}^{}N$($0^{\mathrm{-}}$, 120 keV)→${}^{16}$O($0^{+}$,g.s.)${+\mathrm{e}}^{\mathrm{-}}$ +ν${¯}_{\mathrm{e}}$. A value ${\Lambda }_{\beta }$${(0\mathrm{}}^{\mathrm{-}}$→$0^{+}$)=0.489±0. 020 ${\sec }^{\mathrm{-}1}$ is obtained, which agrees with calculation only when pion exchange currents are included in the nucleon axial current.

The decay of ${}_{{\mathrm{}}^1{\mathrm{}}_{56}^{46}}{}^{}{}_{}{}^{}\mathrm{Ba}_{90}^{}{}_{}{}^{}$ to levels of odd-odd ${}_{{\mathrm{}}^1{\mathrm{}}_{57}^{46}}{}^{}{}_{}{}^{}\mathrm{La}_{89}^{}{}_{}{}^{}$ has been studied in experiments in which γγt coincidence, γγt(θ) angular correlation, γ-ray singles, and time-dependent γ-ray spectra were collected. The ${}_{}{}^{146}{}_{}{}^{}\mathrm{Ba}$ activity was produced directly by on-line mass separation from the fission products of the ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$(${\mathrm{n}}_{\mathrm{th}}$,f) reaction. The half-life of ${}_{}{}^{146}{}_{}{}^{}\mathrm{Ba}$ was determined to be 2.22±0.07 sec. A level scheme containing 48 levels and 231 γ rays is proposed for ${}_{}{}^{146}{}_{}{}^{}\mathrm{La}$. Spin and parity for some levels below 1.2 MeV are assigned on the basis of angular correlation measurements and β-ray branching. Details of the level scheme are discussed within the context of the level systematics of neighboring odd-odd La isotopes and N=89 odd-odd isotones.

Upper limits are derived for the first time on charged, tensor coupling constants that violate time reversal invariance (T). Various previous measurements of beta polarization from nuclear decays are analyzed. The best limit is Im($C_T$$C_A^{\mathcal{’}\mathrm{*}}$+$C_T^{\mathcal{’}}$$C_A^{\mathrm{*}}$) =-0.063±0.052, a factor of 5 more precise than the present limit on analogously-defined, scalar T-violating terms. Finally, the relation of tensor couplings to searches for scalar couplings is discussed. No T violations are inferred.